Spectrum is one of the most costly, on-demand and important resources for wireless communication systems. Cognitive radio has the capability to exploit the utilization of the spectrum by using the available empty spectrum holes temporarily, in an opportunistic manner. The available spectrum can be in the form of a single band (i.e. whole spectrum) or multiple dispersed bands (i.e. dispersed spectrum). Cognitive radio systems currently known in the art utilize the spectrum, for a single user, employing whole spectrum techniques.
In the whole spectrum utilization approach for cognitive radio, the transmit signal occupies a single band as illustrated with reference to FIG. 1. For the whole spectrum utilization system, the baseband signal is processed over a single branch. The baseband transmit signal with absolute bandwidth in the whole spectrum utilization method occupies a whole band. As illustrated with reference to FIG. 2, the baseband signal s(t) is upconverted to the desired carrier frequency, fc, amplified, filtered and then transmitted over the channel. At the receiver side, the received signal is filtered out using a bandpass filter (BPF) with bandwidth of Bwh and downconverted to the baseband.
In prior art systems, the received signal is considered as an orthogonal frequency division multiplexing (OFDM) signal with zero coefficients at the sub-carriers corresponding to the unused bands. Then, the signal can be processed as in a conventional OFDM receiver. However, the available spectrum can be very dispersed in some cases, which requires processing of very large bandwidths if the signal is considered as a single OFDM signal.
Accordingly, what is needed in the art is an improved cognitive transceiver and method of use that does not require the processing of large bandwidths. Such a cognitive transceiver would result in a more efficient communication system.